nas has 2 x 3tb sata 7200rpm & 4 x 2tb sata 5400rpm disks, pulled disk #5 to copy data onto while upgrade was performed.
raid group #1 has 5 disks(2 x 3tb & 3 x 2tb) raid 5 raid group #1 has 2 disks(2 x 3tb) raid 5
You set it up in flexraid mode?
Do you have one volume or two?
Will the system let you switch to xraid?
Also, you should have 5x2TB RAID-5 in the first group, and 2x1TB RAID-1 in the second group.
It looks like you might have tried to add a group instead of choosing expand. Though it is possible that FlexRaid is expecting you to add a 3TB drive. There is a comment in the optimization guide that suggests that:
If your volume has more than one RAID group, you’ll need to add at least 1 drive per RAID group. (page 7)
If the system will let you switch to XRAID, then I think you can just hot-insert the disk, and add it to the array. You'll likely need to format it on the volume tab first.
You could also copy off the data again (this time to a 3 TB drive), and destroy the current volume, and create a new one with 4x2TB+1x3TB using XRAID. Then hot-insert the remainin 3 TB drive.
If you can back up the data, then you could try using ssh to manually expand group 1. @Sandshark can probably give you the commands you'd need - but you'd be on your own, and he can't test them for your specific situation. Doing this incorrectly could easily result in loss of data.
The NAS is clearly confused, as you don't have RAID 50 or 60. Your best bet, if it lets you, is to switch back to XRAID. But, I rather suspect that's not going to work for much the same reason the expand doesn't. There do appear to be some holes in the XRAID logic that have evaded Netgear's testing, and I think some of that same logic is used for FlexRAID expansion. They just can't test every drive combination.
If you post the content of mdstat.log and lsblk.log (from the downloaded log .zip), we can see what you do currently have and whether you can re-add the 2TB via SSH. Please make sure all drives are installed and the NAS is recently re-booted when you download the logs, as drive designations can change on re-boot.
The only issue is that it still may not restore the ability of the NAS to figure out the next expansion step, if there ever is one. So if this is a convenient time to backup, destroy, and restore, it's your best solution.
It may well be the path that's hitting a limitation in the expansion logic, but is giving the wrong error message. I've seen other wrong error messages in my expansion experiments.
